Many disorders affecting children arise from abnormalities in development before birth or from alterations in normal developmental patterns during early childhood. These disorders may be acquired as a response to an insult from the environment or may be inherited via the genetic material from parents. This research proposal concentrates on altered developmental patterns in the formation of muscle structures that are the result of genetic lesions. For experimental purposes, we are performing these studies on a simple roundworm or nematode that contains about 800 cells of which 95 are the muscle cells of interest. These roundworms reproduced about every three days so that the genetic basis of these muscle disorders can be easily deduced. Further, large numbers of these roundworms can be cultivated in the laboratory offerring rich material for electron and light microscopy in this proposal as well as for detailed biochemistry in correlative research programs.